1. Field of the Invention
The invention is a rectification column, comprising a packing and built-in temperature measuring points each with a lead, for determining the temperature profile longitudinally and/or transversely of the column. The invention includes a method for making the column.
A rectification column is used for separating liquid mixtures comprising components with different boiling points, by countercurrent distillation or rectification. In a rectification column, the descending liquid and ascending vapor contact one another in a countercurrent manner. The column is provided with packing which can comprise baffles, metal honeycombs or the like, shaped in a certain way, and which, through their shape, provide for constant, uniform intermixing and interpenetration of the streams as they contact one another.
In the rectification column, heat exchange takes place between the descending liquid and the ascending vapor. The component of higher boiling point present in the vapor is condensed in the descending liquid and the heat of condensation, released in the process, is used to vaporize the component of lower boiling point in the liquid. In this way, the component of lower boiling point accumulates in the vapor and the component of higher boiling point accumulates in the liquid. In addition to the inter-mixing, interpenetration and contact of the vapor and liquid, another important requirement in rectification is of course the maintenance of a certain temperature profile in the column. Losses of heat through the column wall result in cooling of the column wall and hence in an increase in the reflux which, in turn, results in disturbance of the equilibrium of the column. In addition to adiabatic operation, knowledge of the temperature profile inside the column is necessary for optimizing the process.
2. Statement of Related Art
A multiplicity of temperature measuring points are required for determining the temperature profile over the length and the cross-section of a column. In practice, the individual measuring points are either introduced into the interior of the column from outside through openings in the column wall or have been placed in the column from inside through a central tube extending longitudinally through the column. Both systems have disadvantages.
Where the temperature measuring points are introduced from outside through openings in the column wall, each measuring point can only be introduced into the column as far as the periphery of the packing present in the column. The measuring point can only measure the temperature in the peripheral zone of the column. If interior points are to be measured, holes have to be drilled in the packing which can result in damage to the packing and in irregularities in the flow conditions in this zone. Subsequent changes in the arrangement of the temperature measuring points involves considerable expense because a corresponding tube has to be welded into the column and acceptance by a safety authority is required. Another disadvantage of the construction with measuring points introduced into the column from outside, through holes in the column wall, is that the heat insulation surrounding rounding the column has to be removed at each measuring point. Accordingly, each measuring point forms a heat bridge with corresponding heat losses. In addition, removing or replacing the heat insulation material involves considerable extra work at the assembly stage.
Because of the disadvantages involved in use of measuring points introduced from outside through openings in the column wall, attempts have been made to arrange the temperature measuring leads to the particular measuring points in the column, through an internal central tube. In this case, however, temperature measurement is possible only at the outer peripheral zone of the inner tube, not in the main flow regions of the packing. In addition, the full-length inner tube, which can occupy a substantial portion of the column cross-section, can necessitate a correspondingly larger column diameter at extra expense, and can impair the temperature and flow conditions in the column.
The problem addressed by the present invention is to provide a packed column, more particularly a packed rectification column, in which the temperature profile can be measured at any point of the column cross-section over the entire length of the column without the heat insulation, the column wall or the column packing having to be interrupted or damaged and without need for a space consuming central tube with the disadvantages it involves in terms of heat and flow.